Let me first describe by system
Digium 4 port analog card
I have not sip/trunk lines, strictly POTS but when we lose internet our phone system goes wonky. Can’t dial out, can’t transfer or when we put on hold it drops the call etc.
I am using streaming music on hold? Will this make a difference?
Why is this happening and where can I look?
Probably because it has lost DNS service. You probably don’t have in-addr.arpa support (reverse DNS) for your local networks, and it is a getting a temporary failure, rather than a definitive not found, when the external DNS servers are isolated.
Although it relates to the Switchvox product, this thread is relevant:
If it is a DNS issue, you need to provide proper DNS support for your local network when it is isolated.